Use a pthread-based implementation of Itimer.c on iOS
Use a pthread-based implementation of Itimer.c on iOS

Patch from Stephen Blackheath.

timer_create doesn't exist and setitimer doesn't fire on iOS, so we're
using a pthreads-based implementation. It may be to do with
interference with the signals of the debugger. Revisit. See #7723.

mfine/ghc,holzensp/ghc,ml9951/ghc,spacekitteh/smcghc,wxwxwwxxx/ghc,mfine/ghc,mettekou/ghc,ryantm/ghc,vikraman/ghc,mcschroeder/ghc,sgillespie/ghc,elieux/ghc,gridaphobe/ghc,anton-dessiatov/ghc,TomMD/ghc,snoyberg/ghc,hferreiro/replay,hferreiro/replay,lukexi/ghc-7.8-arm64,tjakway/ghcjvm,frantisekfarka/ghc-dsi,ml9951/ghc,tibbe/ghc,lukexi/ghc-7.8-arm64,lukexi/ghc,vikraman/ghc,lukexi/ghc-7.8-arm64,tibbe/ghc,ezyang/ghc,nushio3/ghc,ezyang/ghc,hferreiro/replay,urbanslug/ghc,gcampax/ghc,tjakway/ghcjvm,ekmett/ghc,forked-upstream-packages-for-ghcjs/ghc,acowley/ghc,snoyberg/ghc,frantisekfarka/ghc-dsi,tjakway/ghcjvm,vTurbine/ghc,nushio3/ghc,forked-upstream-packages-for-ghcjs/ghc,GaloisInc/halvm-ghc,TomMD/ghc,nkaretnikov/ghc,urbanslug/ghc,mfine/ghc,christiaanb/ghc,acowley/ghc,elieux/ghc,nushio3/ghc,nathyong/microghc-ghc,sdiehl/ghc,acowley/ghc,olsner/ghc,ezyang/ghc,snoyberg/ghc,tjakway/ghcjvm,wxwxwwxxx/ghc,da-x/ghc,bitemyapp/ghc,gridaphobe/ghc,tibbe/ghc,urbanslug/ghc,ghc-android/ghc,mettekou/ghc,AlexanderPankiv/ghc,ryantm/ghc,vikraman/ghc,tjakway/ghcjvm,hferreiro/replay,nathyong/microghc-ghc,ryantm/ghc,vTurbine/ghc,tjakway/ghcjvm,tjakway/ghcjvm,christiaanb/ghc,wxwxwwxxx/ghc,sdiehl/ghc,nathyong/microghc-ghc,ekmett/ghc,ekmett/ghc,urbanslug/ghc,sgillespie/ghc,TomMD/ghc,oldmanmike/ghc,siddhanathan/ghc,shlevy/ghc,mettekou/ghc,mcschroeder/ghc,holzensp/ghc,olsner/ghc,ml9951/ghc,vikraman/ghc,AlexanderPankiv/ghc,shlevy/ghc,ryantm/ghc,hferreiro/replay,ekmett/ghc,vikraman/ghc,anton-dessiatov/ghc,mcschroeder/ghc,mcschroeder/ghc,forked-upstream-packages-for-ghcjs/ghc,TomMD/ghc,ghc-android/ghc,sgillespie/ghc,anton-dessiatov/ghc,snoyberg/ghc,AlexanderPankiv/ghc,lukexi/ghc,TomMD/ghc,jstolarek/ghc,gcampax/ghc,oldmanmike/ghc,nathyong/microghc-ghc,jstolarek/ghc,elieux/ghc,jstolarek/ghc,da-x/ghc,mettekou/ghc,nkaretnikov/ghc,green-haskell/ghc,forked-upstream-packages-for-ghcjs/ghc,AlexanderPankiv/ghc,AlexanderPankiv/ghc,nathyong/microghc-ghc,fmthoma/ghc,holzensp/ghc,da-x/ghc,nkaretnikov/ghc,nkaretnikov/ghc,holzensp/ghc,forked-upstream-packages-for-ghcjs/ghc,olsner/ghc,hferreiro/replay,GaloisInc/halvm-ghc,gcampax/ghc,ryantm/ghc,olsner/ghc,elieux/ghc,vTurbine/ghc,da-x/ghc,frantisekfarka/ghc-dsi,ekmett/ghc,snoyberg/ghc,vTurbine/ghc,acowley/ghc,bitemyapp/ghc,green-haskell/ghc,sdiehl/ghc,nkaretnikov/ghc,hferreiro/replay,mcschroeder/ghc,siddhanathan/ghc,vikraman/ghc,jstolarek/ghc,shlevy/ghc,mcschroeder/ghc,ezyang/ghc,acowley/ghc,mettekou/ghc,olsner/ghc,mcschroeder/ghc,vTurbine/ghc,acowley/ghc,mettekou/ghc,sgillespie/ghc,bitemyapp/ghc,vTurbine/ghc,elieux/ghc,oldmanmike/ghc,christiaanb/ghc,AlexanderPankiv/ghc,ghc-android/ghc,green-haskell/ghc,GaloisInc/halvm-ghc,da-x/ghc,anton-dessiatov/ghc,green-haskell/ghc,oldmanmike/ghc,frantisekfarka/ghc-dsi,siddhanathan/ghc,shlevy/ghc,TomMD/ghc,gridaphobe/ghc,nushio3/ghc,elieux/ghc,gridaphobe/ghc,shlevy/ghc,ml9951/ghc,olsner/ghc,wxwxwwxxx/ghc,gridaphobe/ghc,AlexanderPankiv/ghc,gcampax/ghc,wxwxwwxxx/ghc,anton-dessiatov/ghc,lukexi/ghc-7.8-arm64,lukexi/ghc-7.8-arm64,spacekitteh/smcghc,da-x/ghc,urbanslug/ghc,christiaanb/ghc,bitemyapp/ghc,forked-upstream-packages-for-ghcjs/ghc,anton-dessiatov/ghc,jstolarek/ghc,lukexi/ghc,ml9951/ghc,gridaphobe/ghc,fmthoma/ghc,forked-upstream-packages-for-ghcjs/ghc,siddhanathan/ghc,nathyong/microghc-ghc,gcampax/ghc,fmthoma/ghc,holzensp/ghc,mfine/ghc,sdiehl/ghc,GaloisInc/halvm-ghc,sdiehl/ghc,ghc-android/ghc,christiaanb/ghc,lukexi/ghc,ezyang/ghc,shlevy/ghc,urbanslug/ghc,oldmanmike/ghc,vTurbine/ghc,gridaphobe/ghc,tibbe/ghc,christiaanb/ghc,nkaretnikov/ghc,mettekou/ghc,spacekitteh/smcghc,olsner/ghc,snoyberg/ghc,christiaanb/ghc,oldmanmike/ghc,GaloisInc/halvm-ghc,ghc-android/ghc,gcampax/ghc,ghc-android/ghc,oldmanmike/ghc,ezyang/ghc,frantisekfarka/ghc-dsi,tibbe/ghc,GaloisInc/halvm-ghc,sgillespie/ghc,TomMD/ghc,gcampax/ghc,vikraman/ghc,ezyang/ghc,elieux/ghc,ghc-android/ghc,ml9951/ghc,wxwxwwxxx/ghc,siddhanathan/ghc,ml9951/ghc,wxwxwwxxx/ghc,nkaretnikov/ghc,mfine/ghc,fmthoma/ghc,GaloisInc/halvm-ghc,siddhanathan/ghc,da-x/ghc,fmthoma/ghc,bitemyapp/ghc,sdiehl/ghc,spacekitteh/smcghc,sgillespie/ghc,acowley/ghc,spacekitteh/smcghc,anton-dessiatov/ghc,mfine/ghc,nathyong/microghc-ghc,fmthoma/ghc,sgillespie/ghc,green-haskell/ghc,mfine/ghc,shlevy/ghc,sdiehl/ghc,fmthoma/ghc,snoyberg/ghc,ml9951/ghc,lukexi/ghc,nushio3/ghc,urbanslug/ghc,nushio3/ghc,siddhanathan/ghc,nushio3/ghc